Linear algebra vectors

  • Thread starter cleopatra
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  • #1
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Homework Statement


F and G are not 0.
F and G are parallel
Proof that F X G is=0


Attempt for a sol:

F=(a1,b1,c1)
G=(a2,b2,c2)
FXG=.....
But then I don´t know how to show that they are parallel.

Or..

Find some numbers for F and G that I know that makes them parallel and show that FXG
are=0
But I think I´m not supposed to use numbers, but a,b,c...

Would you use either one of theses attempts or not?
 

Answers and Replies

  • #2
CompuChip
Science Advisor
Homework Helper
4,302
47
There are several different definitions of vectors being parallel (one of them is that the outer product is zero).
So can you check your notes / textbook and tell us what it means if two vectors are parallel.

If it says something like: "F and G are parallel if there is some number c such that F = c G" then you can simply take
F = (x, y, z)
G = (cx, cy, cz)
and compute the cross product.

(Note that this is completely general because the cross product only exists in 3 dimensions)
 

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